Method of providing a wall around a unitary mass of gas-permeable material for constructing a heat exchanger or a regenerator



M y 1968 J. R. VAN GEUNS ETAL 3,383,751

ITARY MASS OF GAS-PERMEABLE MATERIAL FOR CONSTRUCTING A METHOD OFPROVIDING A WALL AROUND A UN HEAT EXCHANGER -OR A REGENERATOR FiledApril 13, 1965 FIG.2

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INVENTOR JOHANNES R.VAN GEUNS f ADRIANUS P DIRNE I BY AG E 3 mm F UnitedStates Patent 3,383,751 METHOD OF PROVIDING A WALL AROUND A UNITARY MASSOF GAS-PERMEABLE MA- TERIAL FOR CONSTRUCTING A HEAT EX- CHANGER OR AREGENERATOR Johannes Rudolphus van Geuns and Adrianus Petrus Dime,Emmasingel, Eindhoven, Netherlands, as-

signors to North American Philips Company, Inc., New York, N.Y., acorporation of Delaware Filed Apr. 13, 1965, Ser. No. 447,778 Claimspriority, application Netherlands, Apr. 15, 1964, 64-4,045 9 Claims.(Cl. 29-1573) ABSTRACT OF THE DISCLOSURE A method for providing aregenerator with a wall. The regenerator mass is constituted of gauze orfine screening with a wall soldered to the periphery. Since the wall isin excellent contact with the regenerator mass, no leakage occurs.

The invention relates to a method of providing a wall around a packet ofgas-permeable material, for example, a gauze packet, in particular forregenerators or heatexchangers manufactured by this method.

Known heat exchangers and rcgenerators are constructed from agas-permeable mass surrounded by a Wall. In regenerators, theregenerator mass serves for alternately absorbing heat from the mediumwhich performs a reciprocating fiow through the regenerator and thengiving on said heat to the medium again, in heatexchangers thegas-permeable medium serves to effect a better heat-exchange between thewall and the medium.

A drawback of these known constructions is that the connection betweenthe wall and the gas-permeable mass is often insufiicient, so that partof the medium flows along the gas-permeable mass. This is particularlydisadvantageous tor regenerators. For heat-exchangers also this poorconnection is disadvantageous because the thermal contact between themass and the wall becomes worse, as a result of which the heat-exchangeis adversely influenced.

In order to avoid the above poor connection bet-ween the fillingmaterial and the wall it is known to solder the filling material to thewall after enveloping it. In this method, however, there is nopossibility of checking the adherence and it has been found in practicethat many times the filling material was not soldered to the wall atseveral points.

-It is the object of the invention to provide a method with which areadily connecting wall can be provided around a gas-permeable mass.

The method according to the invention is characterized in that a mass ofgas-permeable material is provided at its surface with a layer whichcontains at least one metal and, if desired, one or several otherelements. The layer is subjected to 'a thermal treatment so that ahomogeneous wall is formed.

The gas-permeable mass usually is formed by a number of stacked wirenettings which are thoroughly compressed.

According to the invention, a wall is provided on the surface of thesaid gauze mass. In this case, the wall grows, as it were, on thematerial of the mass, so that the whole surface is thoroughly connectedto the wall. The surprising fact in this case is that during theprovision of the wall the provided material does substantially notpenetrate into the gauze mass but adheres to the surface of the saidmass.

3,383,751 Patented May 21, 1968 The provision of the wall may beeffected, for example, by electrolytic deposition, but it isalternatively possible to manufacture the wall by moulding.

It is of importance, particularly for regenerator-s, that the wall has alow thermal conductivity in the direction of flow of the medium.

In order to accomplish the aforesaid, a further favourable embodiment ofthe method according to the invention is characterized in that theconstituents of the provided layer are chosen so that during the thermaltreatment the said constituents are converted, by diffusion, int-o apoorly heat-conducting alloy.

The constituents of the layer may be the combinations copper-nickel;silver phosphorus; copper-nickel-zinc; copper-silver-phosphorus. Afterdiffusion these combinations give a poorly-conducting material. For someheatexchangers the wall need not be poorly heat-conducting in thedirection of flow. In general, non-alloyed metals will then be chosenfor the material of the wall.

Using the method according to the invention results in a wall whichreadily .joins the filling material and the thermal conductivity ofwhich in the direction of flow is small. A further advantage is that thethickness of the wall may be chosen to be as is desired.

According to a further embodiment of the method according to theinvention the mass of gas-permeable material is provided at its surfacewith layers of different metals, the choice of the said metals beingsuch that after the thermal treatment a comparatively poorlyheat-conducting wall is obtained. According to the invention, theprovided layers may alternatively consist of copper or nickel. These twometals have a ready thermal conductivity. After the thermal treatment,the copper and nickel are converted, by diffusion, into constantan,which has a poor thermal conductivity. Instead of copper and nickel itis alternatively possible to use combinations of other metals or metalalloys. For example, the combinations silver-phosphorus;copper-nickel-zinc; copper-silver-phosphorus readily meet therequirements imposed.

A further favourable embodiment of the method according to the inventionis characterized in that the surface of the mass of gas-permeablematerial has applied thereto a paste of various metal powders and abinder, the metal powders being chosen such that after the thermaltreatment a comparatively poorly heat-conducting metal is formed, afterwhich the formed wall is sealed mechanically by pressure.

A favourable embodiment of the method according to the invention ischaracterized in that the surface of the packet is covered with a pasteof one or several metal metal powders with a hinder, the composition ofthe metal powders being such that after the thermal treatment acomparatively poorly heat-conducting metal is obtained with a meltingrange, the temperature during the thermal treatment lying only slightlyabove the beginning of the melting range.

When the powder consists of several metals, diffusion will occur duringthe thermal treatment while also the powder grains soften on theoutside, as a result of which the grains fuse to a homogeneous tightwall. It is alternately possible to apply already a powder of grains ofthe desired metal on the surface. Naturally, in that case no diffusionwill occur during the thermal treatment, while the grains fuse to atight homogeneous wall. The surprising fact in this case is that it hasbeen found that, during the thermal treatment, the metal powder does notflow away nor is it drawn by capillary action into the mass.

The term metal in this connection is understood to mean herein not onlya metal which consists of one metallic element, but also metal alloyswhich substantially consist of one or several metallic elements, ifdesired mixed with one or several non-metallic elements.

A further favourable embodiment of the method according to the inventionis characterized in that the surface of the mass is covered with a pasteof one or several metal powders and a binder, after which the mass iswrapped with one or several metal wires in a manner such that at leastone closed Winding layer is formed. The layer is then further coveredwith a paste of one or several metal powders, after which the assemblyis subjected to a thermal treatment and the temperature is chosen to behigh so that it lies somewhat above the melting range of the wallmaterial.

In this manner a wall is obtained which, in addition to a poor thermalconductivity in the direction of flow, can demonstrate a sufiicientrigidity against high pressures without it being necessary for thelayers of poorly heat-conducting material to be thick. This is ofparticular importance for heat-exchangers because in this case a wall isdesired which has a low thermal resistance at right angles to thedirection of flow.

In order that the invention may readily be carried into effect, it willnow be described in greater detail with reference to the drawing inwhich several heat-exchangers are shown diagrammatically.

FIGS. 1 to 3 diagrammatically show in cross-section a number ofheat-exchangers having structures in accordance with the teachings ofthe present invention.

In FIG. 1 reference numeral 1 denotes a filling regenerator material inwhich the mass consists of wire nettings built up in layers and pressedon each other. Layers 2 and 3 are deposited by electrolytic depositionon the periphery of this filling material. These layers consistalternately of copper and nickel. After a thermal treatment in whichdiffusion occurs the layers 2 and 3 can no longer be distinguished. Thenthe whole wall has a homogeneous composition, in which, as a result ofthe diffusion, gauze regenerator mass is imbedded in the wall. Thecopper and nickel together have formed constantan. This constantan has apoor thermal conductivity. The filling material 1 is now surrounded by awall which has a particularly good contact with the filling material.

In FIG. 2, a layer 4 is applied on the periphery of the fillingmaterial 1. This layer consists of a paste of metal powders and abinder. The combinations of metal powder may be copper-nickel andcopper-silver-phosphorus. When a thermal treatment is used in which thetemperature lies below the melting point or melting range of the metalpowders, the powders diffuse and a porous wall is formed. By amechanical treatment this wall is sealed by pressure. It isalternatively possible to choose the composition of the powder so thatan alloy with a melting range is obtained. This may be done by mixingpowders of different elements in the correct composition or bypulverizing an existing alloy. By heating just above the melting rangeof the ultimate alloy, the paste flows to a dense, poorly-conductinghomogeneous wall.

FIG. 3 finally shows how first a layer of paste 5 of metal powders isapplied on the surface of the filling material 1. Then a wire 6, forexample, of V A-steel, is wound around the assembly so that a closedwound layer is obtained. A second layer of paste 7 is provided on thewinding layer. Then the assembly is heated so that the layers of paste 5and 7 fuse and diffuse to form dense homogeneous walls with poorlyheat-conducting properties. In this manner a strong wall is obtainedwhich is poorly heat-conducting in the direction of flow of the mediumand, dependent upon the choice of the material of the wire, is readilythermally conducting in the transverse direction.

It has been found that by a correct choice of the metal 70 powders thetemperature of the thermal treatment may be kept low so that sinteringof the gauze mass does not occur.

So with the method according to the invention it has become possible tomanufacture in a comparatively simple manner walls of regenerators andheat-exchangers which are readily joined to the filling material.

What is claimed is:

1. A method of producing a heat exchanger by forming a wall about a massof gas permeable material comprising the steps of applying to thesurface of said mass a layer containing at least one metallicconstituent capable of forming an alloy with said mass, thermallytreating said layer to form a homogeneous wall consisting of said alloybonded to said mass and mechanically pressure sealing said homogeneouswall.

2. A method of securing a mass of gas-permeable material to a heatexchanger wall as claimed in claim 1 wherein the said layer is such thatduring said thermal treatment the said constitutents thereof areconverted into a poorly heat conducting metal alloy by diffusion.

3. A method of securing a mass of gas-permeable material to a heatexchanger wall as claimed in claim 2 wherein the surface of the mass isprovided with a plurality of layers of different metals, said metalsbeing such that after thermal treatment thereof a relatively poor heatconducting wall is formed.

4. A method of securing a mass of gas-permeable material to a heatexchanger wall as claimed in claim 3 wherein said layers consistingalternately of copper and nickel.

5. A method of securing a mass of gas-permeable material to a heatexchanger wall as claimed in claim 1 wherein said layer is applied byelectrolytic deposition on the surface of said mass.

6. A method of securing a mass of gas-permeable material to a heatexchanger wall as claimed in claim 1 further comprising providing abinder, said mass having a paste constituted of at least one metal andsaid binder being applied to the surface of said mass.

7. A method of securing a mass of gas-permeable material as claimed inclaim 1 further comprising providing a binder, said mass having a paste,constituted of at least one metal and said binder being applied to thesurface of said mass, said poor heat-conducting metal being providedwith a melting range, the temperature during said thermal treatmentbeing slightly above the beginning of said melting range.

8. A method of securing a mass of gas-permeable material as claimed inclaim 7 wherein said metal powder is of a relatively poorheat-conducting alloy with a predetermined melting range and saidbinder.

9. A method of securing a mass of gas-permeable material as claimed inclaim 1 wherein the surface of said mass of gas-permeable material iscovered with a first layer of paste of at least one metal power and abinder, wrapping at least one metal wire around said mass and said firstlayer in a manner such that at least one closed winding layer is formed,applying a second layer of paste of at least one metal powder and abinder to said closed winding layer, and subjecting the assembly to saidthermal treatment.

References Cited UNITED STATES PATENTS 2,573,951 11/1951 Brennan29-l82.2 2,993,264 7/1961 Grenoble 29-527 3,081,530 3/1963 VVlodek29-527 3,192,073 6/1965 Jominy et a1. 29-527 3,315,350 4/1967 Kent 29527JOHN F. CAMPBELL, Primary Examiner.

PAUL M. COHEN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,383,751 May 21, 1968 Johannes Rudolphus Van Geuns et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 26, "packet", first occurrence,

should read mass Column 3, line 37, before "gauze" insert the Column 4,line 54, "power" should read powder Signed and sealed this 7th day ofOctober 1969.

(SEAL) Attest:

Edward M. Fletcher, J1. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

